Thermodynamic reciprocating machine with temperature-controlled fuel supply to burner

ABSTRACT

A thermodynamic reciprocating machine comprising a burner device having an inlet for air of combustion to which air of combustion can be supplied by a fan or the like and having a fuel inlet to which fuel originating from a fuel container can be supplied by a fuel pumping device, the outlet of which communicates with the fuel inlet via a fuel supply duct, a fuel return duct being present which at a place at the outlet of the pumping device is connected to the fuel supply duct, a temperature-sensitive element being furthermore present which controls tbe number of revolutions of the pumping device and the fan coupled thereto which each have an output which is directly proportional to the number of revolutions, a pressure control valve which during operation maintains a constant pressure at the outlet of the pumping device being incorporated in the fuel supply duct between the connection plase of the fuel return duct thereto and the fuel inlet, a flow restricting element being incorporated in the fuel return duct.

United States Patent [1 1 Brandenburg Klaus Brandenburg, Kirchen-Wehbach, Germany [75] Inventor:

[73] Assignee: U.S. Philips Corporation, New

York, NY.

[22] Filed: Feb. 24, 1972 [2] Appl. No.: 229,002

[30] Foreign Application Priority Data Mar. 4. 1971 Netherlands 7l0286l [52] U.S. Cl. 60/524, 60/39.27, 60/39.28 T [51 Int. Cl. F23k 5/00, F02g 1/06 [58] Field of Search 60/24, 39.27, 39.28 T, 60/240, 106; 236/15 B [56] References Cited UNITED STATES PATENTS 2.793.497 5/l957 Walter 60/39.46 X 2.949.007 8/1960 Aldrich et al 60/39.46 X 2.984.968 5/l96l Hunter, Jr. et al. 60/240 X 3.094.838 6/l963 Evans 60/39.27 3.l72.254 3/1965 Wright 60/39.27 X

[ Jan.1,1974

3,347,057 10/1967 Wanderham et a]. 60/240 Primary ExaminerMartin P. Schwadron Assistant Examiner-Allen M. Ostrager Att0rney-F rank R. Trifari [57] ABSTRACT A thermodynamic reciprocating machine comprising a burner device having an inlet for air of combustion to which air of combustion can be supplied by a fan or the like and having a fuel inlet to which fuel originating from a fuel container can be supplied by a fuel pumping device, the outlet of which communicates with the fuel inlet via a fuel supply duct, a fuel return duct being present which at a place at the outlet of the pumping device is connected to the fuel supply duct, a temperature-sensitive element being furthermore present which controls the number of revolutions of the pumping device and the fan coupled thereto which each have an output which is directly proportional to the number of revolutions, a pressure control valve which during operation maintains a constant pressure at the outlet of the pumping device being incorporated in the fuel supply duct between the connection plase of the fuel return duct thereto and the fuel inlet, a flow restricting element being incorporated in the fuel return duct.

9 Claims, 5 Drawing Figures PAIENIEUM 11974 I 3.782.120

MN 2 BF 3 r'n N (gr/sec) BACKGROUND OF THE INVENTION The invention relates to a thermodynamic reciprocating machine comprising a burner device having an inlet for air of combustion supplied by means of a fan or the like, and having a fuel inlet supplied by a fuel pump from a fuel container. The fuel pump outlet communicates via a fuel supply duct with the fuel inlet; a fuel return duct is present between the outlet of the pump and the fuel. A temperature-sensitive element is present by means of which the supply of fuel can be controlled, the supply of air of combustion being controlled in proportion of the supply of fuel.

A thermodynamic reciprocating machine of the present type is known from Dutch Pat. Specification 101,166. In this machine, a thermostat influenced by the temperature of the heater operates a control mechanism which is incorporated in the fuel supply duct and which determines the fuel flow to the burner device.

When the power consumption increases, the temperature of the working medium present in the higher temperature part of the working space of the machine and hence the heater temperature decreases. The thermostat then ensures that the control mechanism passes more fuel. When the power consumption decreases, as a result of which the heater temperature increases, the thermostat ensures that the control mechanism passes a smaller fuel flow to the burner device. In this manner a constant heater temperature is ensured.

As measuring places for the temperature-sensitive element are to be considered not only the heater pipes but, for example, the temperature of the working medium is the higher temperature part of the working space may also be determined directly by arranging the temperature-sensitive element in the said space.

In this known device, the control of the supply of air of combustion in proportion to the fuel supply is effected by means of pressure difference gauges which are arranged in the fuel duct and air of combustion duct, respectively, andwhich influence the same member of a hydraulic system in opposite senses, which system actuates controlmechanism in the duct for air of combustion. This known construction for controlling the supply of fuel andair of combustion to the burner device of a thermodynamic reciprocating machine exhibits the drawback of being complicated and expensive (hydraulic control system, control mechanism, pressure difference gauges).

Very high requirements are imposed upon the control mechanism in the fuel duct. As a matter of fact, the passage should be adjustable in an accurate and reproducible manner over a large fuel flow range (for example from 0.02 to 1.2 g/second, i.e., a ratio of l 60 for the smallest to the largest fuel flow). When the imposed requirements are not fulfilled, this gives rise, notably in the case of small fuel flows, to all kinds of difficulties, such as extinguishing of the burner, instabiliity of the temperature control circuit, incomplete combustion of the air-fuel mixture with dirty exhaust gases detrimental to health, all this consequently as "a result of the rate and reproducible manner within a very large measuring range, in which the smallest to the largest pressure difference is in the proportion of l 3,600. Actually, the pressure difference produced according to the flow theorem of Bernouilli is proportional to the square of the rate of flow.

Measuring inaccuracy of the pressure difference gauges results in differences of the ratio air of combustion-fuel from the desirable value, as a result of which incomplete combustion of the air-fuel mixture can occur again.

SUMMARY OF THE NEW INVENTION It is the object of the present invention to provide a thermodynamic reciprocating machine which does not shown any of the above-described drawbacks and in which the air of combustion and the fuel can always be supplied in the correct ratio to the burner device of the machine by means of simple and cheap means.

In order to realize the objective, the thermodynamic reciprocating machine according to the invention is characterized in that the temperature-sensitive element controls the number of revolutions of the pump and the fan coupled thereto which each have an output which is directly proportional to the number of revolutions. A pressure control valve, which during operation maintains a constant pressure at the outlet of the pump, is incorporated in the fuel supply duct between the connection place of the fuel return duct thereto and the fuel inlet, and a flow restricting element is incorporated in the fuel return duct.

In the case of a variation of the temperature of the heater and working medium, respectively, the temperature-sensitive element ensures that both the number of revolutions of the fuel pump and that of the fan which is synchronized with the pump vary, as a result of which a larger or smaller quantity of fuel-and air of combustion is supplied to the burner device. The said numbers of revoultions may be the same or be in a given constant-proportion to each other.

In thermodynamic reciprocating machines, the desirable ratio A air of combustion-fuel is not constant but depends upon the load of the fuel burner in the burnerdevice. This ratio A should decrease when the load of the fuel burner increases, which means that in the case of a lower load a comparatively large excess of air of combustion is necessary and in the case of higher loads a comparatively small excess is necessary. In other words in the case of lower numbers of revolutions of the fuel pump and fan, respectively, in which the outputs are comparatively low and the fuel burner is only slightly loaded, it should be comparatively large, while in the case of higher numbers of revolutions, it should be comparatively small.

A ratio that decreases when the number of revolutions of the fuel pump and fan, respectively, increases, has been realized with simple means in the thermodynamic reciprocating machine according to the invention.

The pressure control valve in the fuel supply duct which during operation maintains a constant pressure at the outlet of the pump, opens when said pressure is reached andonly then passes fuel to the burner device. Since upon opening of the valve the fuel pump operates with a given number of revolutions, hereinafter referred to as the critical number of revolutions, and the fan is coupled to the pump, the fan supplies already air of combustion to the burner device before supply of fuel to said device takes place.

in the case of pressures at the outlet of the pump below the opening pressure of the pressure control valve, respectively in the case of number of revolutions of the pump below the critical number of revolutions, all the fuel supplied by the pump flows back to the fuel container via the fuel return duct. During normal operation, that is to say with the pressure control valve in the open position and with a number of revolutions of the pump above the critical number of revolutions, a constant fuel flow is conducted away through the fuel return duct to the fuel container with a suitable choosen fixed flow restricting element in said return duct irrespective of the number of revolutions then occurring. As a result of this and due to the fact that the characteristics-output-number of revolutions of the fuel pump and fan are linear, it is achieved that the ratio A of air of combustion fuel decreases when the number of revolutions of the said pump and fan, respectively, increases. The linear characteristics may extend mutually in parallel or have mutually different slopes.

In this manner it is possible for the flow of air of combustion and fuel to be always in agreement in such manner that the excess of air in all the operating conditions of the thermodynamic reciprocating machine is just sufficiently large to ensure complete combustion of the air-fuel mixture.

The fuel return duct with flow restricting element need not always be provided separately.

In an advantageous embodiment of the thermodynamic reciprocating machine according to the invention, the fuel return duct with flow restricting element is an integral part of the fuel pump, the pump comprising a cylindrical rotor capable of rotating with a very small amount of play in a cylinder surrounding it, the rotor or the cylinder comprising at least one shallow pumping groove which is situated in a plane transverse to the cylinder axis and which is interrupted in at least one place ofthe circumference by a dam the cylindrical outer surface of which coincides with the cylinder surface of the rotor or the cylinder, a fuel supply communicating with the fuel container opening into the pumpiung groove on one side of the dam, a fuel outlet which communicates with the fuel supply duct communicating with the said groove on the other side of the dam, the fuel return duct with flow restricting element being constituted by the pumping groove. Since the fuel return duct with flow restricting element constitutes in this case as an internal leakage duct an integral part of the pump, a compact construction is obtained.

Upon rotation of the rotor in the cylinder, fuel from the fuel container is taken along by viscous forces from the place where the fuel supply communicates with the pumping groove into the shallow pumping groove and pumped to the place of communication with the fuel outlet. Then the fuel is guided to the fuel supply duct. Such a pumping device supplies a quantity of fuel per unit of time which is directly proportional to the number of revolutions of the rotor and which is independent of the viscosity. The latter is the case because both the internal fuel leak from the fuel outlet to the pumping groove and the flow of fuel to the fuel outlet are inversely proportional to the viscosity of the fuel. This pumping device is not very bulky, a very small dead volume and is extremely simple and reliable.

The pressure control valve serves not only as an auxiliary means in obtaining a desirable ratio A of air of combustion fuel for various load conditions of the burner device and motor, respectively as described above, but it also ensures that the pressure at the outlet of the pumping device is substantially independent of pressure fluctuations which occur in the part of the fuel supply duct adjoining the burner device so that the fuel supplied to said part of the duct experiences no variations by the said fluctuations. The fluctuations may be a result of pressure variations in the atomiser air which become apparent in the fuel supply duct.

It is to be noted that the system of fuel ducts of the thermodynamic reciprocating machine known from the said Dutch Pat. specification 101,166 also comprises a pressure control valve. In this machine, however, it deals with a relief valve which communicates at one end with the outlet of the pumping device and communicates at the other end with the fuel return duct and which maintains the pressure in the fuel supply duct constant by passing a larger or smaller amount of fuel to the fuel return duct. In contrast herewith, in the device according to the invention the pressure control valve is incorporated in the fuel supply duct itself between the connection place of the fuel return duct thereto and the burner device, and said valve maintains the pressure at the outlet of the pumping device at a constant value independently of the pressure in the part of the fuel supply duct present between the control valve and the burner device, which latter pressure varies for the above-mentioned reasons.

In order to ensure in all circumstances that in the thermodynamic reciprocating machine according to the invention, a varied flow of fuel is passed unhindered by the pressure control valve and that the passed flow of fuel is independent of pressure variations occurring in the part of the fuel supply duct communicating with the burner device, a favorable embodiment of the thermodynamic reciprocating machine is characterized in that the pressure control valve comprises a housing having a fuel inlet chamber communicating with the pump and a fuel outlet chamber separated therefrom and communicating with the burner device, a valve seating being arranged between said chambers, a valve body being present which is capable of cooperating with the valve seating and releasing the passage thereof entirely or partly, fuel supplied to the control valve exerting on the valve body a force which is directed away from the valve seating, resilient means being present which exert a force on the valve body in the direction of the seating, said means having a small spring constant for providing a flat fuel pressure-flow characteristic of the control valve, said control valve being furthermore constructed so that forces as a result of the fuel pressure in the outlet chamber exerted on the valve body in a direction away from the seating are small relative to those resulting from the fuel pressure in the inlet chamber.

Since the pressure control valve has a flat pressureflow characteristic, substantially no pressure variation will occur at the outlet of the pumping device upon variation of the flow of fuel by variation of the number of revolutions of the pumping device. The varied fuel flow is then passed without hindrance.

That the fuel in the outlet chamber of the pressure control valve can exert only minor forces on the valve body as compared with the forces exerted thereon by fuel in the inlet chamber, provides the advantage that pressure variations occurring in the outlet chamber have only a small influence on the pressure at the outlet of the pumping device. The pressure variations may originate, for example, from the air which is guided past the atomizer for atomization of the fuel and which is supplied by a special atomizer-air compressor. For any number of revolutions of the pumping device, the flow of fuel supplied to the burner device then is substantially independent of the pressure variations which occur on the side of the pressure control valve facing the burner device.

In order that the invention may be readily carried into effect, it will now be described in greater detail, by way of example, with reference to the accompanying drawings which are diagrammatic and not drawn to scale.

BRIEF DESCRIPTIQN OF THE DRAWINGS FIG. ll shows a thermodynamic reciprocating machine having a burner device which is provided with an air-fuel control;

FIG. 2a shows output-number of revolutions characteristics for a fan and a fuel pump; this Figure furthermore shows which part of the flow of fuel supplied by the fuel pump is going to the burner device and which part is drained;

FIG. 2b shows the ratio A of air of combustion-fuel as a function of the flow of fuel conveyed to the burner device with respect to the curves shown in FIG. 2a;

FIG. 3 shows a fuel pump with an integral fuel return duct with flow restricting element;

FIG. 4 shows an embodiment of a pressure control valve.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference numeral 1 in FIG. 1 denotes a cylinder of a hot gas engine, in which a piston 2 and a displacer 3 can reciprocate with a phase difference. The piston 2 and the displacer 3 are connected to a driving mechanism not shown by a piston rod 4 and a displacer rod 5, respectively. A compression space 6 is present between the piston 2 and the displacer 3, while an expansion space 7 is present above the displacer 3. The compression space 6 and the expansion space 7 communicate with each other via a cooler 8, a regenerator 9 and a heater 10. Via the heater 10, thermal energy can be supplied to working medium in the engine, which medium traverses a closed thermodynamic cycle. The heater 10 is constructed from a number of pipes 11 which communicate at one end with the regenerator 9 and at the other end with an annular duct 12 and a number of pipes 13 which communicate at one end with the annular duct 12 and at the other end with the expansion space 7. The hot-gas engine furthermore comprises a burner device 14 with which communicates an inlet 15 for fuel, an inlet 16 for air of combustion and an outlet 17 for exhaust gases communicating via the heater 10.

The heater 10 comprises a thermocouple 18 as a temperature-sensitive element which determines the heater temperature and the electric signal of which is supplied to an amplifier 19. The number of revolutions of a fuel pump 20 and a fan 21 can be controlled by means of the amplified output signal. Pump 20 and fan 21 are coupled together via a shaft 22. Both the pump and the fan have an output which is directly proportional to the number of revolutions.

The inlet of pump 20 communicates with a fuel container 23 and its outlet communicates via a fuel supply duct 24 with fuel inlet 15 of the burner device 14. At the outlet side of the pump 20, a fuel return duct 25 communicates with its one end at the area 26 with fuel supply ducts 24 and with its other end it opens into fuel container 23.

Between the connection place 26 and the fuel inlet 15 of the burner device 14, a pressure control valve 27 with compression spring 28 and valve body 28' is incorporated in the fuel supply duct 24 and maintains during operation a constant pressure at the outlet of the fuel pump 20. A flow restricting element 29 is incorporated in the fuel return duct 25. The fan 21 furthermore communicates via a supply duct 30 for air of combustion with the inlet 16 for air of combustion of the burner device M.

The operation of the air-fuel control is as follows: When the temperature of the heater 10 decreases, for example, due to increased power consumption, the temperature-sensitive element 18 ensures that the number of revolutions of the fuel pump 20 and the fan 21 coupled thereto is increased so that the quantities of air of combustion and fuel supplied to the burner device per unit of time increase while when the temperature of the heater increases, said element ensures that the number of revolutions decreases so that the quantities of air of combustion and fuel supplied to the burner device per unit of time decrease.

The pressure control valve 28 ensures that fuel can flow to the burner device only from a given number of revolutions of the pump 20, namely at the number of revolutions at which the pressure at the outlet of the pump reaches the opening pressure of the valve 27, which opening pressure is determined by the force which the compression spring 28exerts on the valve body 28. Below this critical number of revolutions, all the fuel supplied by the pump 29 flows via duct 25 with flow restricting element 29 back to fuel container 23.

Above the critical number of revolutions at which the pressure control valve 27 is open and maintains a constant pressure at the outlet side of the pump 20, a constant portion of the flow supplied by the pump 20 flows back to the fuel container 23 via duct 25.

That the return flow is then constant is due to the constant pressure at the inlet of duct 25 at the area 26 and to the constant pressure drop across the fixed flow restricting element 29 (pressure in the container 23 constant). The value of the constant, drained return flow with the pressure control valve 26 in the open position depends upon the choice of the flow restricting element 29.

Both the pump and the fan have linear characteristics for output-number of revolutions. As a result of the linearity of said characteristics and the constant drain return flow with the pressure control valve 27 in the open position, it is achieved that the ratio A air-fuel for the burner device is larger with comparatively low load (small fuel flows) than with comparatively high load. This is of great advantage because, owing to the properties of the fuel burners, a larger excess of air is necessary to ensure complete combustion of the mixture with lower loads than with higher loads.

All this is illustrated in FIGS. 2a and 2b. In FIG. 2a the number of revolutions n is plotted on the horizontal axis and the mass flow rir g/secs.) is plotted on the vertical axis. Curve I relates to the mass flow of air provided by the fanand supplied to the burner device, curve II relates to the mass flow of fuel supplied by the pump of which a constant flow is drained from a given number of revolutions n on (the critical number of revolutions at which the pressure control valve opens) (curve III) and the remainder is supplied to the burner device (curve IV).

By calculating for each value of the mass flow of fuel supplied to the burner device, the ratio supplied mass flow air/fuel and dividing said ratio by the number which indicates how many grams of air are necessary to burn l g of the chosen fuel compeltely (number for which A l), the graph shown in FIG. 2b is obtained in which the ratio A air-fuel versus the mass flow fuel III supplied to the burner device is shown. From this it can be read that decreases when the load increases (larger fuel flows) of the burner device, which is desirable for the above-mentioned reasons.

As fuel pumps having linear characteristics fuel output number of revolutions are to be considered, for example, metering pumps. FIG. 3 shows a viscosity metering pump in which the fuel return duct 25 with flow restricting element 29 of FIG. 1 form an integral part of said pump, so that a very compact construction for the air-fuel control system is obtained. Reference numeral 41 denotes a rotor comprising a shaft 42 which can be coupled to the shaft of the fan of FIG. 1.

The rotor comprises two shallow pumping grooves 43 and 44. The depth of said grooves is, for example 40 /um. The rotor furthermore comprises a considerably deeper outlet 45 the depth of which is, for example, 0.5 mm. The grooves 43 and 44 are each provided with a dam 46 and 47, respectively, in which on one side of said dams the rotor comprises axial supply grooves 48 and 49, respectively, which communicate the relevant grooves 43 and 44 with liquid supplies 48' and 49. On the other side ofthe said dams the rotor comprises axial outlet grooves 50 and 51, respectively, which communicate the grooves 43 and 44 with the outlet duct 45. The rotor fits in the cylinder 52 with a very small amount of play of a few ,um, which cylinder furthermore comprises an outlet 53 which communicates with duct 45, and supplies 60 and 61 which communicate with the ducts 48' and 49.

When the rotor 41 rotates in the direction of the arrow, the liquid in the grooves 43 and 44 is forced in the direction of the axial outlet grooves 50 and 51 by viscous forces, liquid being drawn in from the ducts 48 and 49' via the axial supply grooves 48 and 49. So from the supply grooves 48 and 49 the liquid is pumped through the grooves 43 and 44 to the duct 45 and then flows away through the outlet 53. From the duct 45 some leakage occurs to the grooves 43 and 44 which leakage depends of course on the viscosity of the liquid. Furthermore, in the same manner as the leakage, the outflow resistance through the outlet 53 also depends upon the viscosity. This means that the total supplied liquid flow will be independent of the viscosity and directly proportional to the number of revolutions.

The fuel return duct with flow restricting element in this case consists ofthe pumping grooves 43 and 44, respectively. This is understood as follows: Due to the presence of the pressure control valve 27 on the outlet side of the pump, a constant pressure is impressed upon said outlet side with a number of revolutions above the critical number of revolutions. Consequently, the quantity of fuel supplied by the pump is smaller than it would be in the absence of the said pressure control valve. This may be regarded as a virtual leakage of fuel through the resistance formed by the pumping groove against the direction of pumping. This virtual leakage is proportional to the pressure differential prevailing across the pump. Since said pressure differential is constant, the virtual leakage flow therefore is also constant.

The viscosity metering pump is equally readily useful for gaseous and for liquid fuels while maintaining all the advantages.

In the pump shown, each pumping groove comprises only one dam. In order to obtain an equilibrium of forces for the rotor, it is advantageous to provide each groove with three or more dams which are uniformly distributed on the circumference.

The pressure control valve 27 of FIG. 1 should maintain the pressure on the outlet of the fuel pump 20 as constant as possible because pressure fluctuations result in variations in the quantity of fuel supplied to the burner device. This also means that pressure variations originating from the burner device 14 and which become apparent on the pressure control valve via the fuel supply duct 24 may not influence the pressure on the outlet of the fuel pump 20.

In order to realize this, a pressure control valve as shown in FIG. 4 may be used. This pressure control valve consists of a housing having an inlet chamber 71 and an outlet chamber 72 between which a valve seat 73 is arranged the passage of which can be released and closed, respectively, more or less by a diaphragm 74 as a valve body, which diaphragm is secured to the housing 70. The outlet chamber 72 has an annular duct 72 adjoining the diaphragm 74. A compression spring 75 is furthermore present and exerts a force on the diaphragm 74 in the direction of the valve seating 73 and which has a small spring constant (weak spring). A compression spring 76 is also present which forces the diaphragm 74 against the housing 70.

Fuel supplied to the inlet chamber 71 exerts a force on the diaphragm 74 which tends to displace said diaphragm in the direction remote from the valve seating 73.

Owing to the slackness of diaphragm 74, a small variation in the fuel pressure in the inlet chamber results in a comparatively large displacement of the diaphragm and hence a comparatively large variation in the passed fuel flow.

Due to the large area of diaphragm 74 which is subject to the fuel pressure in the inlet chamber 71 as compared with the diaphragm area which is subject to the fuel pressure in the outlet chamber 72, the latter plays no significant part in the play of forces on the diaphragm and a variation in the fuel pressure in the outlet chamber has substantially no influence on the pressure in the inlet chamber. Pressure variations originating from the burner device 14 then have no influence on the pressure on the outlet of fuel pump 20 and on the flow of fuel supplied to the burner device.

If, in order to obtain a flow of fuel which is independent of variations in the viscosity, a viscosity pump as the one described here is used, the pressure metering which maintains the pressure control valve may possibly not be kept constant but be varied in accordance with the viscosity. This can be achieved by using a bimetal compression spring which exerts a force on the diaphragm 74 of FIG. 4 varying with the ambient temperature. Even more complete but more expensive is the solution in which a second viscosity metering pump rotates with a constant number of revolutions and, with the same fuel as that which is supplied to the burner device, exerts a force on the diaphragm 74 in the direction of the valve seating 73 instead of the compression spring 75.

What is claimed is:

1. In a thermodynamic reciprocating machine operable with a source of fuel and air, and including a burner having an air inlet and a fuel inlet, and a heater heated by the burner, the improvement in combination therewith of a rotary fan supplying air from said source to said air inlet, a rotary fuel pump supplying fuel from said source to said burner fuel inlet, the fan and pump each having a flow output directly proportional to the rotors number of revolutions, means for driving said fan and pump simultaneously at the same speed, a temperature-sensitive element registering the temperature of the heater and providing a corresponding control signal for controlling said speed of the fan and pump, the pump having an outlet and a fuel supply duct from said outlet to said burner fuel inlet, a pressure control valve in said fuel supply duct intermediate said burner inlet and the pump outlet for maintaining constant pressure of fuel flow therethrough, a flow junction in said fuel supply duct intermediate said valve and said pump outlet, a fuel return duct from said junction to said fuel source, a flow restricting element in said return duct, whereby, the temperature-sensitive element when registering a higher temperature causes slower speed of said fan and pump and vice versus, and said control valve provides a greater air fuel ratio 7 as said speed is increased and total output of said pump and fan is increased.

2. Apparatus according to claim 1 wherein said fuel pump comprises a housing with acylindrical bore and axis, a cylindrical rotor that rotates within said bore and about said axis with adjacent bore and rotor surfaces having a close fit, first, second, and third circumferential grooves axially'and sequentially spaced apart in one of said surfaces, the first being a liquid supply groove, the second a pumping groove, the third an outlet groove, also in said surface an axial supply groove communicating said first and second grooves and an axial outlet groove communicating said second and third grooves, said third groove being slightly deeper than the second groove, means for communicating fuel from the fuel supply to said liquid supply groove, and means for communicating fuel from said outlet groove to said fuel supply duct, said pumping groove constituting said fuel return duct and flow restricting element.

3. ln a thermodynamic reciprocating machine operable with a source of fuel and air, and including a burner having an air inlet and a fuel inlet, and a heater heated by the burner, the improvement in combination therewith of a rotary fan supplying air from said source to said air inlet, a rotary fuel pump supplying fuel from said source to said burner fuel inlet, the fan and pump each having a flow output directly proportional to the rotors number of revolutions, means for driving said fan and pump simultaneously at the same speed, a temperature-sensitive element registering the temperature of the heater and providing a corresponding control signal for controlling said speed of the fan and pump, the pump having an outlet and a fuel supply duct from said outlet to said burner fuel inlet, a pressure control valve in said fuel supply duct intermediate said burner inlet and the pump outlet for maintaining constant pressure of fuel flow therethrough, a flow junction in said fuel supply duct intermediate said valve and said pump outlet, a fuel return duct from said junction to said fuel source, a flow restricting element in said return duct, whereby, the temperature-sensitive element when registering a higher temperature causes slower speed of said fan and pump and vice versus, and said control valve provides a greater air fuel ratio y as said speed is increased and total output of said pump and fan is increased wherein said fuel pump comprises a housing with a cylindrical bore and axis, a cylindrical rotor that rotates within said bore and about said axis with adjacent bore and rotor surfaces having a close fit, first, second, and third circumferential grooves axially and sequentially spaced apart in one of said surfaces, the first being a liquid supply groove, the second a pumping groove, the third an outlet groove, also in said surface an axial supply groove communicating said first and second grooves and an axial outlet groove communicating said second and third grooves, said third groove being slightly deeper than the second groove, means for communicating fuel from the fuel supply to said liquid supply groove, and means for communicating fuel from said outlet groove to said fuel supply duct, said pumping groove constituting said fuel return duct and flow restricting element.

4. Apparatus according to claim 2 wherein all of said grooves are in the rotors outer circumferential surface.

5. Apparatus according to claim 2 wherein all of said grooves are in said bore surface.

6. Apparatus according to claim 6 wherein said housing has a first duct having one end receiving fuel from said fuel supply and a second end terminating as an aperture in said bore surface discharging to said supply groove, and a second duct having one end terminating as an aperture in said bore surface for receiving fuel from said outlet groove and a remote end for discharging to said fuel supply duct.

7. Apparatus according to claim 2 wherein said second groove has depth of approximately 40/um and said third groove has depth of approximately 0.5m.

8. Apparatus according to claim 2 further comprising fourth and fifth circumferential grooves situated axially and sequentially with respect to said first, second, and third grooves, the fourth groove being a pumping groove substantially the same as said second groove, the fifth groove being a supply groove substantially the same as said second groove, and a second axial supply groove communicating the fourth and fifth grooves, and a second axial outlet groove communicating said fourth and third grooves, and further means communicating said fuel supply with said fifth groove, whereby forces on the rotor are axially balanced.

9. Apparatus according to claim 1 wherein said pressure control valve comprises a housing defining therein separate fuel inlet and outlet chambers, which communicate respectively with said pump and burner inlet, and a passage interconnecting said chambers, the passage including a valve seat, valve means operable with said seat to releasably seal and separate said chambers, resilient means urging said valve means to remain sealed, whereby fuel supplied to said inlet chamber tends to open said valve, said resilient means having a small magnitude spring constant for providing a substantially flat fuel pressure-flow characterisic, said valve being opened when said fuel pressure in the inlet chamber is greater than pressure of said resilient means.

. UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patent No. 3,782,120 7 Dated January 1, 1974 Inven tor 9 KD U BRANDENBURG It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

' Col. 1, line 13, after "fuel" inser t --supply duct-- Col. 2, line 55, after "ratio" insert --;i Col. 6, line 27, cancel while" Col. 7, line 32', before "/u m"' deleize line' 43, before u m" delete Claim 6, delete "6 and insert ---4--- Claim 7, line 2, u m" should be u m- Signed and sealed this 16th day of July 1974.

(SEAL) Attest: v v

McCOY M. GIBSON, JR. I C. MARSHALL DANN Attesting Officer Commissioner of Patents 

1. In a thermodynamic reciprocating machine operable with a source of fuel and air, and including a burner having an air inlet and a fuel inlet, and a heater heated by the burner, the improvement in combination therewith of a rotary fan supplying air from said source to said air inlet, a rotary fuel pump supplying fuel from said source to said burner fuel inlet, the fan and pump each having a flow output directly proportional to the rotor''s number of revolutions, means for driving said fan and pump simultaneously at the same speed, a temperature-sensitive element registering the temperature of the heater and providing a corresponding control signal for controlling said speed of the fan and pump, the pump having an outlet and a fuel supply duct from said outlet to said burner fuel inlet, a pressure control valve in said fuel supply duct intermediate said burner inlet and the pump outlet for maintaining constant pressure of fuel flow therethrough, a flow junction in said fuel supply duct intermediate said valve and said pump outlet, a fuel return duct from said junction to said fuel source, a flow restricting element in said return duct, whereby, the temperature-sensitive element when registering a higher temperature causes slower speed of said fan and pump and vice versus, and said control valve provides a greater air fuel ratio gamma as said speed is increased and total output of said pump and fan is increased.
 2. Apparatus according to claim 1 wherein said fuel pump comprises a housing with a cylindrical bore and axis, a cylindrical rotor that rotates within said bore and about said axis with adjacent bore and rotor surfaces having a close fit, first, second, and third circumferential grooves axially and sequentially spaced apart in one of said surfaces, the first being a liquid supply groove, the second a pumping groove, the third an outlet groove, also in said surface an axial supply groove communicating said first and second grooves and an axial outlet groove communicating said second and third grooves, said third groove being slightly deeper than the second groove, means for communicating fuel from the fuel supply to said liquid supply groove, and means for communicating fuel from saiD outlet groove to said fuel supply duct, said pumping groove constituting said fuel return duct and flow restricting element.
 3. In a thermodynamic reciprocating machine operable with a source of fuel and air, and including a burner having an air inlet and a fuel inlet, and a heater heated by the burner, the improvement in combination therewith of a rotary fan supplying air from said source to said air inlet, a rotary fuel pump supplying fuel from said source to said burner fuel inlet, the fan and pump each having a flow output directly proportional to the rotor''s number of revolutions, means for driving said fan and pump simultaneously at the same speed, a temperature-sensitive element registering the temperature of the heater and providing a corresponding control signal for controlling said speed of the fan and pump, the pump having an outlet and a fuel supply duct from said outlet to said burner fuel inlet, a pressure control valve in said fuel supply duct intermediate said burner inlet and the pump outlet for maintaining constant pressure of fuel flow therethrough, a flow junction in said fuel supply duct intermediate said valve and said pump outlet, a fuel return duct from said junction to said fuel source, a flow restricting element in said return duct, whereby, the temperature-sensitive element when registering a higher temperature causes slower speed of said fan and pump and vice versus, and said control valve provides a greater air fuel ratio gamma as said speed is increased and total output of said pump and fan is increased wherein said fuel pump comprises a housing with a cylindrical bore and axis, a cylindrical rotor that rotates within said bore and about said axis with adjacent bore and rotor surfaces having a close fit, first, second, and third circumferential grooves axially and sequentially spaced apart in one of said surfaces, the first being a liquid supply groove, the second a pumping groove, the third an outlet groove, also in said surface an axial supply groove communicating said first and second grooves and an axial outlet groove communicating said second and third grooves, said third groove being slightly deeper than the second groove, means for communicating fuel from the fuel supply to said liquid supply groove, and means for communicating fuel from said outlet groove to said fuel supply duct, said pumping groove constituting said fuel return duct and flow restricting element.
 4. Apparatus according to claim 2 wherein all of said grooves are in the rotor''s outer circumferential surface.
 5. Apparatus according to claim 2 wherein all of said grooves are in said bore surface.
 6. Apparatus according to claim 4 wherein said housing has a first duct having one end receiving fuel from said fuel supply and a second end terminating as an aperture in said bore surface discharging to said supply groove, and a second duct having one end terminating as an aperture in said bore surface for receiving fuel from said outlet groove and a remote end for discharging to said fuel supply duct.
 7. Apparatus according to claim 2 wherein said second groove has depth of approximately 40 Mu m and said third groove has depth of approximately 0.5m.
 8. Apparatus according to claim 2 further comprising fourth and fifth circumferential grooves situated axially and sequentially with respect to said first, second, and third grooves, the fourth groove being a pumping groove substantially the same as said second groove, the fifth groove being a supply groove substantially the same as said second groove, and a second axial supply groove communicating the fourth and fifth grooves, and a second axial outlet groove communicating said fourth and third grooves, and further means communicating said fuel supply with said fifth groove, whereby forces on the rotor are axially balanced.
 9. Apparatus according to claim 1 wherein said pressure control valve comprises a housing defining therein separate fuel inlet and outlet chambers, which communicate respEctively with said pump and burner inlet, and a passage interconnecting said chambers, the passage including a valve seat, valve means operable with said seat to releasably seal and separate said chambers, resilient means urging said valve means to remain sealed, whereby fuel supplied to said inlet chamber tends to open said valve, said resilient means having a small magnitude spring constant for providing a substantially flat fuel pressure-flow characteristic, said valve being opened when said fuel pressure in the inlet chamber is greater than pressure of said resilient means. 